Vu An Thanh, Feinberg David A
San Francisco VA Health Care System, San Francisco, CA, United States.
Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States.
Front Psychol. 2021 Jul 20;12:690198. doi: 10.3389/fpsyg.2021.690198. eCollection 2021.
Speed-accuracy tradeoff (SAT) theory dictates that decisions can be made more quickly by sacrificing accuracy. Here we investigate whether the human brain can operate in a brief metabolic overdrive to overcome SAT and successfully make decisions requiring both high levels of speed and accuracy. In the context of BOLD fMRI we expect "a brief metabolic overdrive" to involve an increase in cerebral oxygen metabolism prior to increased cerebral blood flow-a phenomenon known as the "initial dip" which results from a sudden drop in oxyhemoglobin in perfusing blood. Human subjects performed a motion discrimination task consisting of different difficulties while emphasizing either accuracy (i.e., without time pressure) or both speed and accuracy (i.e., with time pressure). Using simultaneous multi-slice fMRI, for very fast (333 ms) measurement of whole brain BOLD activity, revealed two modes of physiological overdrive responses when subjects emphasized both speed and accuracy. The majority of subjects exhibited the hypothesized enhancement of initial dip amplitude in posterior visual cortex (PVC) with the size of the enhancement significantly correlated with improvement in behavioral performance. For these subjects, the traditionally analyzed post-stimulus overshoot was not affected by task emphasis. These results demonstrate the complexity and variability of the BOLD hemodynamic response. The discovered relationships between BOLD response and behavior were only observed when subjects emphasized both speed and accuracy in more difficult trials suggesting that the brain can perform in a state of metabolic overdrive with enhanced neural processing of sensory information specifically in challenging situations.
速度-准确性权衡（SAT）理论表明，通过牺牲准确性可以更快地做出决策。在这里，我们研究人类大脑是否可以在短暂的代谢超速状态下运作，以克服速度-准确性权衡并成功做出需要高水平速度和准确性的决策。在血氧水平依赖性功能磁共振成像（BOLD fMRI）的背景下，我们预计“短暂的代谢超速”会在脑血流量增加之前涉及脑氧代谢的增加——这是一种被称为“初始下降”的现象，它是由灌注血液中氧合血红蛋白的突然下降引起的。人类受试者在强调准确性（即没有时间压力）或速度和准确性两者（即有时间压力）的同时，执行了由不同难度组成的运动辨别任务。使用同步多层功能磁共振成像对全脑BOLD活动进行非常快速（333毫秒）的测量，结果显示当受试者强调速度和准确性两者时，存在两种生理超速反应模式。大多数受试者在视觉后皮层（PVC）表现出假设的初始下降幅度增强，增强的大小与行为表现的改善显著相关。对于这些受试者，传统分析的刺激后过冲不受任务重点的影响。这些结果证明了BOLD血流动力学反应的复杂性和变异性。仅在受试者在更困难的试验中强调速度和准确性两者时，才观察到所发现的BOLD反应与行为之间的关系，这表明大脑可以在代谢超速状态下运行，特别是在具有挑战性的情况下增强对感觉信息的神经处理。
